I was wondering if disabling vlan 1 on a switch does not forward all traffic from a SPAN source interface to the destination interface. For security reason, I shutdown the vlan 1 interface (as it was not needed), but when I want to monitor the traffic going through an interface on the switch it only passes the UDP, CDP, and other types of traffic but none of the TCP traffic is showing up on the destination interface. Both, RX and TX are configured on the source interface and everything else looks good as far as the session configuration.
Please let me know if having vlan 1 turned off could be causing the problem or not.
you are unable to access the switch, the management VLAN interface (VLAN 1 is the default management VLAN interface) might have been shut down or has not had an IP address assigned to it. If the VLAN interface is shut down, you may need to connect using a console cable and then configure the VLAN interface. You can then verify that the management VLAN interface is properly IP addressed and not in a shut down state.
The problem was not with the configuration of the SPAN session but with ethereal. For some reasons, ethereal has a hard time capturing the TCP traffic off a SPAN session. I put a different traffic analyzer and everything was going through.
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